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        CLIC\MONITOR delta_time


    This command is used to prepare the atmospheric phase  correction  based
    on  the  total  power  monitor (normally done at 1.3 mm). It process all
    scans in the current index and performs two operations.

    First, it processes the calibration scans to compute the correction fac-
    tors. i.e. the change of path length for a given change in emission tem-
    perature of the atmosphere at the atmospheric monitor frequency (normal-
    ly  1.3  mm,  i.e.  using Receiver 2 data). These correction factors are
    then written in subsequent scans, until a new calibration is found.

    Second, the scans in the current index are grouped in intervals of maxi-
    mum duration `delta_time' (in seconds); source changes will also be used
    to separate intervals. In each interval a straight line is fitted in the
    variation  of atmospheric emission as a function of time; this line will
    be the reference value for the atmospheric correction, i.e. the  correc-
    tion at time t is proportional to the difference between the atmospheric
    emission at time t and the reference at time t. This scheme is  used  to
    avoid  contaminating the correction with total power drifts of non-atmo-
    spheric origin (changes in receiver  noise  and  gain,  and  changes  in
    ground noise).

    MONITOR 0 will use for each scan the average of the atmospheric emission
    as the reference value. This will cause the correction to average to ze-
    ro  in one scan: the average phase is not changed, only the coherence is
    restored leading to an improved amplitude (this is what is done  in  the
    correlator  at the Plateau de Bure to compute the scan-averaged spectral
    and continuum quantities).

Gildas manager 2018-02-21